Link for an excavating chain and associated excavating chain

ABSTRACT

A link for an excavating chain for a ballast excavating device below a railroad track, the link comprising a body extending longitudinally between a front end and a rear end and being crossed by at least one front through-hole and a rear through-hole configured to receive hinge means with an adjacent link of the chain, the front and rear through-holes extending along axes parallel to each other and contained in a reference plane of the body, the link further comprising, on an inner side of the body with respect to the reference plane opposite to the outer side, a concave guide surface extending over an envelope having an axis generator parallel to the axes of the link joints, the guide surface being configured to at least locally match a curvature of a return member of the excavating device.

TECHNICAL FIELD OF THE INVENTION

The invention relates, in general, to the technical field of clearing or excavating chains.

The invention relates more specifically to a link for an excavating chain intended to travel on a travel path having a rectilinear excavating portion for a ballast clearing device below a railroad track, and to an excavating chain comprising such links.

PRIOR ART

Work trains equipped with machines designed for removing the ballast located under the sleepers of a railroad track, and sorting it for possible reuse by dumping it on the track, are known from the prior art. These machines are commonly referred to as “strippers.” In a known manner, such work trains generally comprise a machine designed for screening the ballast in order to preserve, on the one hand, the good part of the ballast for its reuse and, on the other hand, to remove the worn part of the ballast in wagons provided for this purpose. In this way, the stripper-screener makes it possible to remove, sort the used ballast and replace the entire layer of ballast with the sorted good ballast as well as any additional supply of new ballast.

Such work trains are equipped with excavating chains consisting of a succession of links articulated together, at least part of which being equipped with scoops intended to excavate the ballast. This chain is arranged in a displaceable or height-adjustable manner on the chassis of the railway vehicle. The chain is moved in an endless manner by a drive mechanism. The path of the chain is configured so that it has a straight excavating portion located under the sleepers of the railroad track, the chain working on this excavating portion transversely to the orientation of the rails of the railway by dragging and carrying the ballast with it. Brackets forming return members for the excavating chain are arranged on either side of this rectilinear excavating portion. These brackets are located at the ends of the rectilinear excavating portion along which the ballast is removed, and are generally formed of an elbow-shaped attached wall on which the chain links slide successively. The chain travels along a longitudinal inbound path, then over the rectilinear excavating portion after passing through a first elbow-shaped portion formed by one of the brackets. The chain, which continues on its way, then leaves said rectilinear excavating portion to travel on the longitudinal outbound portion after having crossed a second elbow-shaped portion formed by another of the brackets. The scoops arrive unloaded on this rectilinear excavating portion and come out loaded with ballast towards the longitudinal outbound portion. The longitudinal inbound and outbound portions are connected, in an area located overhead relative to the railway vehicle, by a transverse dumping portion where the ballast is dumped onto conveyor belts. The scoops unloaded from the ballast then continue their way towards the inbound longitudinal portion and then repeat these operations.

These scoops are designed to meet many problems. In particular, they must be strong enough to ensure a certain number of predetermined cycles in order to ensure the excavating and transport of ballast while requiring a minimum of maintenance. These scoops must also allow the efficient transportation of the ballast towards its dumping point in view of the screening operation so as to improve the performance of the stripper as regards the excavation of the ballast as well as that of the screener as regards the re-use rate of good ballast.

Despite these objectives, and given the considerable forces undergone by excavating scoops, improving their resistance in order to minimize their maintenance is a constant problem and improvements are continuously sought.

To further extend their life, it is also known to provide these scoops with reinforced fingers forming claws and placed in the extension of the scoop. Such fingers are designed to be highly resistant, their maintenance being easier than that of the links of the chain itself, which makes it possible to adapt more precisely to localized wear according to the forces undergone. Thus, this allows to reduce maintenance cost and shorten maintenance time, resulting in shorter machine downtime.

However, the wear of the links is also localized at the return members. Indeed, the shocks undergone in these elbow-shaped zones, taking into account the forces involved, often lead to premature wear at the brackets, and, more generally, at the return members arranged along the path traveled by the chain. The wear is also localized on the inner side of the links, opposite to the outer side from which the scoop projects.

DISCLOSURE OF THE INVENTION

The invention aims to remedy all or part of the drawbacks of the state of the art by proposing, in particular, an excavating chain allowing to reduce the wear of its links, and also allowing to reduce the wear undergone by the return members.

To achieve this objective, according to a first aspect of the invention, it is proposed a link for an excavating chain intended to travel on a travel path having an excavating portion for a ballast clearing device below a railroad track, the link comprising a body extending longitudinally between a front end and a rear end and being crossed by at least one front through-hole and a rear through-hole configured to receive hinge means with an adjacent link of the chain, the front and rear through-holes extending along axes parallel to each other and contained in a reference plane of the body, the link being characterized in that the body comprises, on an inner side of the body with respect to the reference plane, opposite to the outer side, a concave guide surface extending over an envelope having an axis generator parallel to the axes of the link, the guide surface being configured to, at least locally, match a curvature of a return member of the clearing device.

Thanks to such a combination of characteristics, the link can travel on a return member such as brackets on either side of a rectilinear excavating portion, locally following its curvature. In this way, wear both on the inside of the link and on the return member is reduced.

Furthermore, during such a movement, the link is stabilized by a surface contact between the guide surface of the body of the link, on the one hand, and the drive surface of the return member, on the other hand, which locally has a substantially complementary shape. Indeed, such a surface contact makes it possible to avoid a rotation of the link around itself during the passage of the drive member, as occurs when a vertical rectilinear line contact takes place between the link and the return member. Such stabilization aims to improve the efficiency of ballast transport by the scoop. Such a configuration also allows to reduce the noise produced by the clearing device.

Contrary to popular belief, such a characteristic involves a relief on the inside of the body of the link so that a person skilled in the art might think that it would be likely to slow down the movement of the chain which carries it, on the one hand, and cause premature wear, on the other hand. This is not the case and experience has shown that the use of such a link does offer better passage over the return members on either side of the rectilinear excavating portion.

According to a particular technical characteristic, the guide surface extends along a directing curve having, at least locally, the shape of an elliptical arc, and preferably of a circular arc. Such a configuration offers a progressive continuous curvature for the passage of the return member.

According to one embodiment, the distance separating two front and rear longitudinal ends of the guide surface is greater than the distance separating the front and rear through-holes, or even greater than the distance between the front and rear through-holes.

In a particularly advantageous configuration, the guide surface extends between its two front and rear longitudinal ends, the front and rear ends each being located substantially in line with the front and rear through-hole, respectively. Preferably, this end is positioned in line with an intermediate zone delimited between, on the one hand, a longitudinal end portion of the through-hole located towards the inside of the body and, on the other hand, its central axis.

According to one embodiment, the body of the link comprises, on its inner side, preferably in line with each of the front and rear through-holes, a convex surface extending between the concave guide surface and the associated front or back end of the link body. This allows a better passage of the return members when arriving on them. The combination of these convex surfaces bordering the concave surface is particularly reliable in limiting the wear of the link bodies and the return members, while limiting the noise caused by the movement of the chain. To ensure continuity between the convex surfaces and the concave guide surface, these convex surfaces each extend over an envelope having an axis generator parallel to that of the concave guide surface.

In an advantageous configuration, the front and rear ends of the body each have a curved convex portion, preferably in the form of a circular arc so as to be free of edges. This configuration provides effective and lasting protection of the joints of the chain links against wear by abrasion by ballast stones with sharp or cutting edges and against the action of dust, thus conferring a longer life of the chain links. This curved portion preferably extends over an envelope having a generator parallel to the axis of the associated through-hole.

In a particular technical configuration, the link comprises a projecting part extending from an outer side of the body with respect to the reference plane. The projecting part comprises for example a scoop for transporting ballast.

According to one embodiment, the scoop has a stop surface configured to receive a counter-stop from an adjacent rear link of the chain so as to limit a relative rotation between the chain link and the adjacent rear link around the axis of the rear through-hole. Such a counter-stop is particularly effective on the rectilinear excavating portion along which the scoops work and undergo a force exerted by the ballast, generating a moment on the scoop tending to cause the scoop, and therefore the link body, to pivot backwards. The counter-stop makes it possible to limit the effect of this moment of forces applied to the scoop so that the associated link continues its path in a straight line.

In a particular technical configuration, at least one of the through-holes, configured to receive hinge means with an adjacent link of the chain, has a flat surface so as to block an axis of the hinge means from rotating.

According to an advantageous characteristic, the link comprises fingers born by the scoop and projecting outwards from the outer side of the reference plane in the extension of the scoop. These fingers are preferably each oriented along an axis inclined with respect to the reference plane, with an inclination preferably between 65 and 80°, preferably between 70 and 75°. This allows the use of shorter fingers to lighten the scoop without losing performance or losing rigidity.

According to one embodiment, the fingers are all located above a plane perpendicular to the parallel axes of the front and rear through-holes and tangent to a lower end of said scoop. This increases the life of the fingers.

According to one embodiment, the projecting part comprises a counter-stop configured to come into abutment against a stop surface of a scoop of an adjacent front link so as to limit a relative rotation between the link and the adjacent front link around the axis of the front through-hole.

According to one embodiment, the body is unitary, i.e., in one piece, preferably produced by foundry, with or without machining of the front and rear through-holes and/or the guide surface.

The invention also relates to a finger for a scoop of a link of an excavating chain intended to travel on a travel path having an excavating portion for a device for clearing ballast below a railroad track, the finger comprising a plurality of grooves configured to receive a blocking member to ensure adjustment of the finger in translation relative to the scoop. Thus, the position of the blocking member in one of the grooves determines the axial position of the finger relative to the scoop.

Such fingers may equip scoops as described above, but also any other scoop of the prior art whose fingers are attached by such blocking members, independently of the characteristics of the link body.

According to another aspect of the invention, the latter relates to an excavating chain having an excavating portion for a device for clearing ballast below a railroad track, the excavating chain being characterized in that it comprises a succession of chain links comprising all or part of the aforementioned characteristics to form an endless chain.

According to one embodiment, the chain links comprise links of the type having a projecting part, preferably links of the type comprising a scoop and links of the type having a counter-stop, and links of the type without projecting part. Preferably, the excavating chain comprises a succession of a plurality of chain links forming the same pattern which is repeated successively placed end-to-end along the chain, such a pattern comprising from the front to the rear in the travel direction of the chain: a link of the type comprising a scoop, a link of the type comprising a counter-stop, a link of the type without a projecting part, then a link of the type comprising a counter-stop.

According to another aspect, the invention also relates to a device for clearing ballast comprising such an excavating chain, the excavating chain preferably being moved in an endless manner by a drive mechanism and being guided on its travel path at least by bevel gears, the body having, on an inner side of the body with respect to the reference plane, opposite to the outer side, a concave guide surface extending over an envelope having an axis generator parallel to the axes of the joints of the link, the guide surface following, at least locally, a curvature of at least one of the return members of the excavating device, preferably at least two return members arranged on either side of the excavating portion.

According to one embodiment, a radius of curvature of the guide surface is equal, at least locally, to a radius of curvature of at least one of the return members, preferably at least of the two return members. arranged on either side of the excavating portion.

BRIEF DESCRIPTION OF FIGURES

Other characteristics and advantages of the invention will become apparent on reading the following description, with reference to the appended figures, which illustrate:

FIG. 1 : a simplified side diagram of a work train equipped with a stripper-screener according to one embodiment;

FIG. 2 : a partial diagram of an excavating or clearing device according to this embodiment, seen from the front without an excavating chain;

FIG. 3 : a front view of a portion of an excavating chain according to one embodiment, at a return member at one end of a rectilinear excavating portion;

FIG. 4 : a top view of the excavating chain portion according to the embodiment of FIG. 3 , at a return member at one end of a rectilinear excavating portion;

FIG. 5 : a detailed profile view of a chain link provided with a scoop according to this same embodiment;

FIG. 6 : a front perspective view of a chain link provided with a scoop according to this same embodiment;

FIG. 7 : a rear perspective view of a chain link provided with a scoop according to this same embodiment;

FIG. 8 : a perspective view of a reinforcing finger of a scoop according to one embodiment;

FIG. 9 : a rear perspective view of a chain link equipped with a scoop according to this embodiment, and equipped with reinforcing fingers in accordance with FIG. 8 ;

FIG. 10 : a top view of a portion of an excavating chain according to another embodiment;

FIG. 11 : a perspective view of the excavating chain portion according to the embodiment of FIG. 10 .

For greater clarity, identical or similar elements are identified by identical reference signs in all of the figures.

DETAILED DESCRIPTION OF AN EMBODIMENT

FIG. 1 shows a railway vehicle 1 such as a stripper-screener equipped with a clearing or excavating device 4 to clean the ballast of a railroad track 2. This clearing or excavating device 4 is arranged between two bogies 3 of train 1.

The ballast clearing device 4 comprises an excavating chain 8 moved in an endless manner by a drive mechanism 9 and guided by ducts including a transverse duct 5 located under the track 2 in the working position, along which the chain travels over a substantially rectilinear excavating portion 8A. The clearing device 4 further comprises riser and down ducts 6, 7 connected on either side of the transverse duct 5 to which they are connected by elbow-shaped portions forming return members 40 also called “brackets” (see FIG. 2 ). It is understood that the excavating portion is substantially rectilinear, even if excavating is ensured in a part of the curve of each of the bevel gears.

The drive device 9 is arranged overhead relative to the railway vehicle 1, above the railroad track 2, on one side longitudinally opposite to the transverse duct 5, and between the riser duct 6 and the down duct 7. The drive device 9 is placed on the path of the excavating chain 8 and comprises a drive wheel 9′ meshing locally with links 100 of the excavating chain 8 so as to move it. Thus, there is formed an endless path to guide the excavating chain 8. Arrows illustrated in FIG. 2 indicate the travel direction of the chain 8. At the upper ends of the riser 6 and down ducts 7, on the side of the drive device, idler wheels 41 forming return members 40 are provided to ensure the correct travel of the chain 8 at these elbow-shaped zones.

Once the ballast is transported overhead in the riser duct 6, it is unloaded on a conveyor belt 10 and then transported to a screening unit 11 in order to sort the good ballast from the worn ballast.

The vehicle 1 further comprises a lifting unit 13 of the railroad track 2 which is connected to a frame 14 of the vehicle 1 and which is located upstream of the device 4 for clearing or excavating with respect to a work direction 12 of the vehicle 1. A height adjustment device 16 is also provided and connected to the frame 14 of the vehicle 1, which is configured to move the clearing device 4, by drive means 15, from a raised position to a lowered position under the railroad track 2, said clearing device 4 being optionally connected, for example in a removable manner, to the transverse duct 5 by a connector (not shown in the figures).

According to one embodiment FIGS. 3 and 4 illustrate front and top views, respectively, of part of the excavating chain 8. This part of the excavating chain 8 is located at a return member 40 connecting one end of a rectilinear excavating portion 8A of the chain 8 guided by the transverse duct 5, and the inlet of the outbound longitudinal portion 8B guided by the riser duct 6. This return member 40 is formed of an elbow-shaped attached surface at an angle substantially equal to 90° so that it forms a square.

The excavating chain 8 is formed of a succession of links 100 articulated in pairs until the two ends of the chain 8 are connected end-to-end to form a closed, endless-type chain 8.

Each of the links 100 comprises a body 101 which extends longitudinally between a front end 110 and a rear end 120, respectively provided with at least one front hole 111 and a rear hole 121 passing right through the link 100 and configured to receive hinge means with an adjacent link of the chain 8. The longitudinal direction is understood here as the travel direction of the link 100. The front 111 and rear 121 through-holes extend along axes parallel to each other and contained in a reference plane P of the body 101, each link 100 comprising a projection 130, 140 extending from an outer side 100A of the body 101 of the link 100 with respect to the reference plane P.

The projections of the links 100 may comprise a scoop 130 for transporting ballast, or a counter-stop 140 configured to abut against a stop surface 131 of a scoop 130 of an adjacent front link 100 so as to limit a relative rotation between the link 100 of chain 8 and the adjacent front link around the axis of the front through-hole 111. As illustrated in particular in FIG. 4 , the excavating chain 8 is composed of an even number of links 100, the links 100 of the type comprising a scoop 130 and the links 100 of the type comprising a counter-stop 140 being arranged successively in an alternating manner along the chain 8. In this way, each link 100 comprising a scoop 130 has a stop surface 131 located at the back of the scoop 130 and is configured to receive a counter-stop 140 from an adjacent rear link of the chain 8 so as to limit a relative rotation between the link 100 of chain 8 and the adjacent rear link around the axis of the rear through-hole 121. Such a stop position of the scoop 130 against the counter-stop 140 of the associated rear link 100 is shown in FIG. 4 , at the link 100 located on the rectilinear excavating portion 8A. Indeed, along this portion 8A, the scoops 130 undergo a force when driving the ballast which generates a moment on the scoop 130 which tends to tilt the link 100 backwards, this tilting resulting in a pivoting of the scoop 130 around the axis A2 of the rear through-hole 121 configured to receive hinge means 160. To further limit this pivoting around the axis A2 of the rear through-hole 121, at least one of the through-holes 111, 121 has a flat surface 105 so as to block the axis A1, A2 of the associated hinge means 160 in rotation.

The flat surface 105 of each axis is oriented so as to be contained in a plane perpendicular to the reference plane P and parallel to an axis A1, A2 of the associated through-hole 111, 121. Such an orientation of the flat surface 105 of the axes makes it possible to improve blocking in rotation of the axis in question, the force being on the flat surface of the axis.

The hinge means 160 are formed in this embodiment by axes passing through a rear through-hole 121 of a link 100 and front through-hole 111 of another link 100, the axis being blocked in translation by a circlip positioned in an inner groove of the through-hole. The circlip groove is machined into the scoop 130 to allow it to be held in place in its housing. In this embodiment, the links 100 comprising scoops 130 are outer links of the chain 8 or female links in that they have a body 101 comprising a front end 110 and a rear end 120 each provided with two side plates of predetermined thickness between which is inserted a centered plate of a front 110 or rear 120 end of a body 101 of a link 100 comprising a counter-stop 140, thus forming inner link 100 or a male link. The axis of the hinge means 160 is configured to be housed in the corresponding through-hole formed by the alignment of through-hole portions of each of these three plates.

Along this rectilinear excavating portion 8A, the links 100 run transversely relative to the railroad track 2 which corresponds to the longitudinal direction of the bodies 101 of the links 100 on this portion. The links 100 are oriented so that the axes A1, A2 of the through-holes 111, 121 are substantially vertical with respect to the ground, the reference plane P then being vertical, and the scoop 130 or the counter-stop 140 extending substantially radially outward 100A of the body 101 of the link 100.

In this embodiment, the links 100 are made, for example, of manganese steel and made in one piece. An example of a process for manufacturing this link 100, produced by foundry, comprises at least one step of injecting metal, and in particular a step of molding in a mold formed, for example, of a form and an associated counter-form.

As can be seen more particularly in FIG. 5 , each link 100 comprises, on an inner side 100B of the body 8 of the link 100 with respect to the reference plane P, opposite to the outer side 100A, a concave guide surface 150 extending over an envelope 155 having an axis generator G (see FIG. 7 ) parallel to the axes of the joints A1, A2 of the link 100. This guide surface 150 is configured to match, at least locally, a curvature C of a return member 40 of the clearing device 4 (see FIG. 4 ).

The bevel of the return member 40 has a convex rounded surface connecting two surfaces arranged at 90° relative to each other. The guide surface 150 extends along a guiding curve Cd having the shape of a circular arc. In the plane of FIG. 5 , the guiding curve Cd follows the envelope 155.

The guide surface 150 extends between two front 151 and rear 152 longitudinal ends of said guide surface 150, the distance d which separates them being greater than the distance D1 separating the front 111 and rear 121 through-holes. This distance d may also be greater than the center distance D2 between the through-holes (not shown).

According to the embodiment illustrated in detail in FIGS. 3 to 9 , the front 151 and rear 152 longitudinal ends of the guide surface 150 are each located substantially in line with an intermediate zone Zi (see FIG. 5 ) delimited between the central axis A1, A2 of the associated through-hole 111, 121 and the inner edge of the corresponding through-hole 111, 121, this intermediate zone Zi extending longitudinally over a distance corresponding to a radius of the associated through-hole 111, 121. The inner edge of the through-hole 111, 121 is understood to mean a longitudinal end portion of the through-hole 111, 121 located towards the inside of the body 101 of the link 100.

The link 100 also comprises, on the inner side 100B of its body 101, in line with each of the axes A1, A2 of the front 111 and rear 121 through-holes, a convex surface 153, 154 extending between the concave guide surface 150 and the associated front 110 or rear 120 end of the body 101 of the link 100. This allows a better passage of the return members 40 arriving on them. The combination of these convex surfaces 153, 154 bordering longitudinally on either side of the concave surface 150 is particularly reliable for limiting the wear of the bodies 101 of the links 100 and of the return members 40 while limiting the noise caused by the movement of the chain 8.

To ensure continuity between the convex surfaces 153, 154 and the concave guide surface 150, these convex surfaces 153, 154 each extend over an envelope having an axis generator parallel to that of the concave guide surface 150.

Therefore, outside of the return members 40, the links 100 are guided by the corresponding ducts, resting on the path by two bearing zones of the link 100 which are located on these convex surfaces 153, 154, namely at the outside of the concave part delimited by the guide surface 150 and in longitudinal overlap of the front 111 and rear 121 through-holes. Such a location of these bearing surfaces formed by these convex surfaces 153, 154 also makes it possible to avoid a rearward tilting of the scoop 130 in the bevel of the return members due to changes in direction.

In order to ensure effective and lasting protection of the joints of the links 100 of the chain 8 against wear by abrasion by the ballast and against the action of dust, thus conferring a longer life of the links 100 of the chain 8, the front 110 and rear 120 ends of the link 100 each have a curved convex portion 112, 122, for example in a circular arc, so as to be free of edges. Each curved portion 112, 122 preferably extends over an envelope having a generator parallel to the axis of the associated through-hole. For these same advantages, the guide surface 150 is preferably chamfered on its side edges 156.

Each link 100 provided with a scoop 130 for excavating and transporting ballast comprises fingers 132 born by the scoop 130 and projecting outward from the outer side 100A of the reference plane P, in the extension of the scoop 130. In this embodiment, there are three of these fingers 132: a central finger, a lower finger and an upper finger. The fingers 132 are made of high-strength steel, for example, and one end 132 a is arranged projecting in the extension of the scoop 130.

Each finger 132 has a cylindrical body 132 b configured to cooperate in a tubular receptacle 134 provided for this purpose and at least one radial groove 132 c on its cylindrical body 132 b. The groove 132 c is dimensioned so as to receive a blocking member 135 such as a screw penetrating substantially orthogonally with respect to the finger 132 in the tubular receptacle 134 and penetrating at least partially in the groove 132 c. In this way, the blocking member 135 is configured to block the cylindrical body 132 b in translation relative to the tubular receptacle 134 of the scoop 130, the blocking member 135 extending tangentially with respect to a bottom of the groove 132 c. These fingers 132 make it possible to protect the scoop 130 from wear, in particular at its end and in the lower part of the scoop 130 where the wear is generally greater. As illustrated in FIG. 8 , the fingers 132 may include a plurality of grooves 132 c to allow adjusting the finger 132 in translation and thus causing it to translate in its tubular receptacle 134 to assume predetermined positions depending on its wear.

The fingers 132 are removably attached relative to the scoop 130, the removal of the blocking means 135, for example by unscrewing it, making it possible to unlock the finger 132 concerned and remove it from its tubular receptacle 134 by translating it. The blocking means 135 may also be secured by any suitable means such as a pin (not shown in the figures).

The fingers 132 are each oriented along an axis inclined with respect to the reference plane P, with an inclination a of between 65 and 80°, preferably between 70 and 75°.

The fingers 132 are also oriented in a plane P132 inclined relative to a mean plane P130 of the scoop 130 extending substantially vertically (see FIG. 4 ), the inclination a being preferably between 20 and 35°, and being equal to approximately 30° in this embodiment. Such a characteristic makes it possible, in comparison with an equivalent useful working surface of a scoop 130 with an inclination which would be greater, to lighten the scoop 130 without losing performance or losing rigidity. The useful working surface of the scoop 130 is understood here as the surface swept by the scoop 130 during its travel.

The fingers 132 are all located above a Pinf plane perpendicular to the parallel axes of the front 111 and rear 121 through-holes and tangent to a lower end of said scoop 130, in particular in this embodiment, also below a plane Psup tangent to an upper end of the scoop 130 (see FIG. 9 ). Given the orientation of the chain 8 and therefore of the scoop 130 on the rectilinear excavating portion 8A, the planes Pinf and Psup are generally horizontal. This lower end is sensitive in that it is extremely stressed in terms of wear by abrasion against the ballast so that if the wear becomes too severe, this can harm the correct attachment of the fingers 132 to the back of the scoop 130. With a lower finger 132 located entirely above the Pinf plane, a longer service life is ensured for the link 100. Preferably, the hardness of the lower surface of the scoop 130 is increased by adding chromium/manganese and vanadium by welding, or by adding tungsten carbide plates, for example.

FIGS. 10 and 11 illustrate an excavating chain according to another embodiment. In the same way as previously described, the excavating chain 8 is formed of a succession of links 100 articulated two by two until the two ends of the chain 8 are connected end-to-end to form a closed, endless-type chain 8.

This embodiment essentially differs from the other embodiments illustrated in that the chain 8 comprises links without any projecting part. The bodies 101 of each of the links are similar, in particular each link 100 comprises, on an inner side 100B of the body 8 of the link 100 with respect to the reference plane P, opposite to an outer side 100A, a guide surface 150 which is configured to match, at least locally, a curvature C of a return member 40 of the clearing device 4.

As illustrated in FIGS. 9 and 10 , the excavating chain 8 is composed of a succession of links 100 among which the links are of three different types: the links 100 of the type comprising a scoop 130, the links 100 of the type comprising a counter-stop 140 and the links 100 of the type without a projecting part, i.e., formed essentially of their body 101.

The function of such links 100 without a projecting part is mainly to lighten the excavating chain 8. Another function is to better adapt the volume of excavated ballast to the maximum capacity of the screen without losing too much of its own capacity, which is reduced by approximately 20%, and not 50% as a person skilled in the art might think, because of the substantially doubled spacing between two scoops 130 in such a configuration. This is possible, in particular, thanks to the geometry of the scoop 130 similar to that described above, and in particular its inclination.

In this embodiment, each of the links 100 of the type comprising a scoop 130 is located between two links 100 of the type comprising a counter-stop 140. In addition, each link 100 of the type without a projecting part is also located between two links of the type comprising a counter-stop 140. Therefore, every other link is provided with a counter-stop 140, the other links being alternately a link of the type comprising a scoop 130 and a link of the type without a projecting part.

Therefore, a pattern of the chain is formed by a link 100 of the type without a projecting part interposed between two links of the type comprising a counter-stop 140, and a link 100 of the type comprising a scoop 130 at a front or back end of this set of three links: these four links 100 form together, and in this order, a pattern which is repeated successively along the chain 8.

Such a configuration has several advantages. Each link 100 comprising a scoop 130 comes directly in front of a link comprising a counter-stop 140 so as to limit, as already described, a relative rotation of the link carrying the scoop 130. Furthermore, in order to reduce the number of types of links 100, the attachment interfaces between their bodies 101, at their front 110 and rear 120 ends, are identical for a link 100 of the same type: the links comprising a scoop 130 and the so-called “intermediate” links without a projecting part are so-called “female” links for their connection in chain 8, and the links 100 comprising a counter-stop 140 are so-called “male” links for their connection in chain 8.

As described above, the female links have a body 101 whose front 110 and rear 120 ends are each provided with two side plates or flanges of predetermined thickness between which is inserted a centered plate of a front 110 or rear 120 end of a body 101 of another adjacent link 100. The axis of the hinge means 160 is configured to be housed in the associated through-hole formed by the alignment of through-hole portions of each of these three plates of the two links, nested one inside the other so as to form a hinge. In order to improve the resistance of the intermediate link 100, namely without a projecting part, this link 100 has a convex surface on an outer side 100A of the body 101 with respect to the reference plane P, opposite to the inner side 100B. Such a surface aims to increase the distance separating the surfaces of the inner 100B and outer 100A sides of the body 101, i.e., to increase the thickness of the body 101 of the links to make them more resistant. The guide surface 150 is, for its part, always configured to match, at least locally, a curvature C of a return member 4 of the excavating device 4.

Obviously, the invention is described above by way of example. It is understood that a person skilled in the art is able to produce different variant embodiment of the invention without departing from the scope of the invention. 

1. A link for an excavating chain intended to travel on a travel path having an excavating portion for a ballast excavating device below a railroad track, the link comprising; a body extending longitudinally between a front end and a rear end and being crossed by at least one front through-hole and a rear through-hole configured to receive hinge means with an adjacent link of the chain, the front and rear through-holes extending along axes parallel to each other and contained in a reference plane of the body, the link being characterized in that the body has, on an inner side of the body with respect to the reference plane, opposite to the outer side, a concave guide surface extending over an envelope having an axis generator parallel to the axes of the link, the guide surface being configured to match a curvature of a return member of the excavating device.
 2. The chain link of claim 1, wherein the guide surface extends along a guiding curve having at least partially the shape of an elliptical arc.
 3. The link for an excavating chain of claim 1, wherein the distance separating two front and rear longitudinal ends of the guide surface is greater than the distance separating the front and rear through-holes, and preferably greater than the center distance between the front and rear through-holes.
 4. The link for an excavating chain of claim 1, wherein the front and rear ends of the body each have a curved convex portion free of edges.
 5. The link for an excavating chain of claim 1, wherein the link comprises a projecting part extending from an outer side of the body with respect to the reference plane.
 6. The link for an excavating chain of claim 1, wherein the projecting part comprises a scoop for transporting ballast.
 7. The link for an excavating chain of claim 6, wherein the scoop has a stop surface configured to receive a counter-stop of an adjacent rear link of the chain so as to limit a relative rotation between the link of chain and the rear adjacent link around the axis of the rear through-hole.
 8. The link for an excavating chain of claim 1, wherein at least one of the through-holes configured to receive hinge means with an adjacent link of the chain has a flat surface so as to block an axis of the hinge means in rotation.
 9. The link for an excavating chain of claim 5, characterized in that the link has fingers born by the scoop and projecting outward from the outer side of the reference plane in the extension of the scoop, and fingers oriented along an axis inclined with respect to the reference plane, with an inclination preferably between 65° and 80°, preferably between 70 and 75°.
 10. The link for an excavating chain of claim 9, wherein the fingers are all located above a plane perpendicular to the parallel axes of the front and rear through-holes and tangent to a lower end of said scoop.
 11. The link for an excavating chain of claim 1, wherein the projecting part comprises a counter-stop configured to come into abutment against a stop surface of a scoop of a front adjacent link to limit relative rotation between the link of chain and the front adjacent link around the axis of the front through-hole.
 12. The link for an excavating of claim 1, wherein the body is in one piece, produced by foundry, with or without machining of the front and rear through-holes or the guide surface.
 13. An excavating chain having an excavating portion for a ballast excavating device below a railroad track, the excavating chain comprising a succession of links of chain.
 14. The excavating chain of claim 13, wherein the links of chain comprise links of the type comprising a projecting part, comprising a scoop comprising a counter-stop, or links of the type without a projecting part.
 15. A device for excavating or clearing ballast comprising an excavating chain, the excavating chain being guided on its travel path at least by bevel return members, the body having on an inner side of the body with respect to the reference plane, opposite to the outer side, a concave guide surface extending over an envelope having an axis generator parallel to the axes of the link, the guide surface matching, at least locally, a curvature of at least one of the return members of the excavating device.
 16. The chain link of claim 2, wherein the guide surface extends along a guiding curve having at least partially the shape of a circular arc.
 17. The link for an excavating chain of claim 4, wherein the distance separating two front and rear longitudinal ends of the guide surface is greater than the distance separating the front and rear through-holes, and greater than the center distance between the front and rear through-holes.
 18. The link for an excavating chain of claim 11, wherein the link fingers are oriented along an axis inclined with respect to the reference plane, with an inclination between 70° and 75°. 